Friday, NASA marks the anniversary with tributes to the crew of Columbia and 10 other astronauts lost in the space agency's two previous fatal accidents -- the 1986 explosion that destroyed Columbia's sister ship Challenger, and the launch pad fire that killed Apollo 1's three-man crew in 1967. All three anniversaries fall within a week -- the Apollo fire on January 27, Challenger on January 28 and Columbia on February 1.

In this handout photo by NASA, the floor of the RLV Hangar is full of pieces of Space Shuttle Columbia debris delivered from the search and recovery efforts in East Texas on May 8, 2003 at the Kennedy Space Center, Florida.

Controllers lost contact with Columbia at 8:59 a.m. ET, about 15 minutes before it had been expected to land at the Kennedy Space Center at Cape Canaveral, Florida. Shuttle commander Rick Husband's wife Evelyn, who was waiting for him there, feared the worst.

Commemorations will also be held in some of the towns where the orbiter's wreckage rained down that bright Saturday morning. One of them is Hemphill, Texas, about 170 miles north of Houston, where a roadside monument and a museum commemorate the disaster and the volunteers who combed the surrounding woods for pieces of the spacecraft.

"Some of them, you knew instantly what they were," said Belinda Gay, one of those searchers. "We would find some of the instrument panel that was in the shuttle cockpit. You could still see the numbers and the switches. You knew that if you found a can of caviar with Velcro on the back of it, you know it's not supposed to be in the woods."

The remains of the shuttle's crew were found near Hemphill, along with the nose, part of the landing gear and much of the cabin. In addition, two members of a helicopter crew engaged in the search were killed in a crash the following month.

Gay now leads the Sabine County Columbia Memorial Committee. Unlike Steed, whose space buff sister-in-law called her outside that morning, she was getting ready for a relative's baby shower and didn't see the breakup.

"My house started vibrating, and the pictures on the wall started shaking, and then I heard two sonic booms," she said. "We knew something was up."

Gay's husband was president of the local Veterans of Foreign Wars chapter, and she led the group's Ladies' Auxiliary. Hemphill's VFW hall was quickly turned into a dining hall for the search teams, and it will host lunch for the guests at Friday's ceremony.

Overall, NASA recovered about 84,000 pieces of the orbiter, about 40% of the craft, scattered from the Texas panhandle to Fort Polk, Louisiana. Pieces turned up as late as 2011, when the state's brutal drought uncovered an aluminum fuel tank on the bottom of Lake Nacogdoches.

An investigation determined Columbia was doomed almost from the instant its 16-day mission began. A piece of insulating foam from its external fuel tank broke away, striking and cracking a panel on the orbiter's left wing. The damaged panel allowed searing hot gases to seep into the wing on re-entry, causing the craft to lose control and disintegrate.

The three surviving shuttles returned to space starting in 2005. The last mission was in 2011, thirty years after Columbia -- the first of the class -- made its maiden voyage.

NASA and the families of the crew decided to preserve its wreckage, which now sits on the 16th floor of the massive Vehicle Assembly Building at Cape Canaveral. For scientists, it's a "treasure trove" that lets them study the material used in the spacecraft, said Mike Ciannilli, the caretaker of the orbiter's remains.

And for young NASA workers, it's a place to see firsthand why failure can't be an option.

"When you actually walk amongst Columbia and you talk about the accident and you talk about the lessons learned and how you can do the best job you can do to help prevent this from ever happening again, that's very powerful," Ciannilli said.